A high-level, very casual, and often self-deprecating look at trends in catches of Tyee salmon in Campbell River’s legendary Tyee Pool. All data exploration is being completed for fun and to learn some new tools (namely R Markdown and plotly).
There are far more technical ways of examining this data, but they aren’t as much fun - and are frankly hard. This analysis is living and will evolve over time. All results and interpretation are purely speculative and should be considered nothing more than ramblings of a fish nerd.
Normally this is where I would put pictures of all the beautiful Tyee
I have captured, but that hasn’t happened yet. So far, these are the
best things I have managed to get in my boat
I have compiled the following datasets to use in this analysis. Whether they are all incorporated is yet to be seen.
This is certainly an interesting dataset, especially given it is the centenary of the Tyee Club, but it has its limitations. For example, there is no accessible information on effort (# boats per day), biological data (e.g. size, girth and age of tyees) or numbers of non-tyee salmon captured in the pool.
There are lots of ways to look at this data. I am most curious about three things:
How total catches vary among years and if they fluctuate relative to escapement.
When are Tyees most frequently captured?
Has fish size changed across seasons? Does fish size vary within seasons?
Figure 1: Trends in Tyee Salmon captures and Campbell River Chinook Salmon escapement.
A quick look at Tyee catches (blue vertical bars) in Figure 1 shows:
If we look at Escapement data (blue line) shown in Figure 1 , we can see:
Now, lets see when fish are most frequently captured throughout the season, and if there has been a change over time.
Figure 2: Cumulative tally of Tyee’s captured by decade. Note
that values for 2023 are incomplete and only current to August 15,
2023.
The Tyee season runs from July 15 to September 15. I need to pick my battles with my wife and boss. Let’s see which days I should be fighting for!?
Let’s see when the first Tyee are most frequently captured each season. Alright, looks like I should have fished tonight (August 1) and need to fish August 6. Note that values for August 2 and August 7 are somewhat misleading as the plot is showing the number of fish captured on opening day.
Figure 3: Number of Tyee captured on date when first Tyee is registered.
Figure 4: Total fish captured by date and decade
This plot will become a lot more interesting once I can get my hands on some historical data. But for now, we can see:
OK, well now we know not to bother fishing until early August, that I should book the off the last 3 weeks of August and that odds are that 2023 is not going to set a new record for most Tyee’s captured. But who knows.
Figure 5: Mean annual weight of Tyee Salmon captured since 2002.
So overall mean fish size is relatively consistent across years. That’s good news, but maybe there are better ways to look at this data. Bar plots can be deceptive.
Figure 5: Mean annual weight of Tyee Salmon captured since 2002.
Well that is a bit better. The overall mean size of Tyee has stayed relatively stable across years, which makes sense given there is a minimum size limit for Tyee - but there also appears to fewer bigger fish being captured each year.
Figure 6: Weight of Tyee salmon caught per day since 2002.
What a mess. Pretty hard to identify any relationships from that figure.
Historic catch record data is available back to 1923, but only for newly registered members. So any fish captured by existing members are excluded. Either way, the data set still includes over 2880 records and offers a peak into the historic size range of fish captured in the Tyee pool.
If we plot the mean weight for each year we get the figure below which shows a fairly strong decreasing trend in fish size since about 1950.
Figure 7: Mean annual weight and SE of all fish recorded in the record book since 1923.
Given the variability in the number of fish that were captured each year, lets try to standardize the process by selecting a random sample of 10 fish from each year (or all fish if less than 10 were registered in a year). This produces the figure below. Which also shows a strong decreasing trend in fish size since the late 1940’s and early 1950’s.
Figure 8: Mean annual weight and SE of 10 randomly selected fish recorded in the record book since 1923.
To round this out, let’s just have a look at the total number of fish caught per day over the past 20 years.
Figure 4: Total fish captured by date and decade
Without additional data there is not much else to look at. So let’s change gears and start poking around at what may be contributing to observed patterns in catches and size.
(* more like what have others learned about Chinook in the Campbell, I don’t know much).
There has been a lot of information collected on Campbell River Chinook Salmon, including from Tyee Salmon captured in the Tyee Pool, however, most of this data is not readily available online. Data that is available (and that I have found) is summarized below. Data and study results from other systems have also been included for comparison and emphasis.
Figure 9: Chinook Salmon escpaement in the Campbell and Quinsam rivers from 1991 to 2021.
The origin of fish captured in the tyee pool was determined by examining coded wire tags in adipose clipped fish and otoliths in non-clipped fish captured between 2015-2018 CRSF 2018. This data suggests the majority of captured fish in the pool (including undersize) are from the Quinsam Hatchery (mean = 61% across all years), followed by the Discovery Passage Seapens (mean = 17% across all years). The remaining 6% of fish are intercepted on route to natal streams (e.g. Big Qualicum, Nitinat, Washington State hatcheries).
Despite 79% of all captured fish having an adipose fin, only 16% were actually wild and not of hatchery origin. Meaning most hatchery fish were not visually marked (but did have thermal otolith marking), which is not surprising given resources required for fin clipping.
Ages calculated from a subset of otoliths of fish captured in the tyee pool between 2015-2018 (n = 48) shows that the majority of fish are Age-4 (overall mean = 75%), followed by Age-5 (17%) and Age-3 (8%). No Age-6 fish were identified in the sub-sample of heads that were aged.
Of the 350 fish captured in the Tyee pool between 2015 and 2018, 26% were Tyee salmon (n = 90). However, this varied between years with Tyee representing 18% to 32% of all fish captured between years.
A roughly equal proportion of spawners return to the Campbell River as age-4 and age-5 fish (see Table 1) Sturham et al. 1999. Very few fish return as Age-6 (1% (1 of 99 fish) of Campbell River fish in Sturham dataset.
However, Ewart & Anderson,2013 report that Age-5 fish were dominant in 2012 (61%), with Age-4’s accounting for only 37% of the run, and age-3’s representing only 2%. Age-6 fish were absent from the 2013 dataset.
catch_data %>% filter(Year >=2015, Year <=2018) %>%
group_by(Year) %>%
summarize(total.catch = sum(catch_binary))
## # A tibble: 4 × 2
## Year total.catch
## <chr> <dbl>
## 1 2015 15
## 2 2016 13
## 3 2017 44
## 4 2018 18
| Waterbody | Age | n | % of Total | Size Range (mm) |
Mean Lenght (mm) |
|---|---|---|---|---|---|
| Campbell River | 3 | 6 | 7.9 | 500 - 699 | 595.0 |
| Campbell River | 4 | 34 | 44.7 | 550 - 949 | 779.5 |
| Campbell River | 5 | 35 | 46.1 | 700 - 949 | 842.5 |
| Campbell River | 6 | 1 | 1.3 | 900 - 949 | 930.0 |
| Quinsam Hatchery | 3 | 76 | 20.2 | 400 - 749 | 619.5 |
| Quinsam Hatchery | 4 | 225 | 59.8 | 550 - 899 | 743.5 |
| Quinsam Hatchery | 5 | 73 | 19.4 | 700 - 949 | 834.0 |
| Quinsam Hatchery | 6 | 2 | 0.5 | 750 - 849 | 784.0 |
| Quinsam River | 3 | 46 | 22.8 | 500 - 849 | 663.0 |
| Quinsam River | 4 | 114 | 56.4 | 550 - 949 | 733.5 |
| Quinsam River | 5 | 40 | 19.8 | 700 - 949 | 818.0 |
| Quinsam River | 6 | 2 | 1.0 | 800 - 849 | 838.0 |
Interesting side notes on recent studies examining trends in size of Chinook salmon.
According to Ewart & Anderson (2013), female Chinook returning to the Campbell River in 2012 carried roughly ~5,700, a decrease from the roughly 6,000 eggs typically carried.
Decreasing fecundity rates have also been reported in larger studies. For example, Malick et al. 2023 compiled 2.5 decades worth of broodstock data from 43 hatcheries to examine trends in fecundity. They found significant declines in fecundity (and length), with the greatest drop in fecundity occurring over the past decade. This reduction in fecundity was primarily explained by a reduction in the size of spawners. Not particularly relevant, but they also estimate that a 1 mm reduction in length results in ~7.8 few eggs per female
Estimates of juvenile Chinook production based on numbers of observed spawners have generally been less than numbers trapped throughout the out-migration period (Thornton et al. 2022), suggesting juvenile survival rates may be above average (e.g. >10%).
Juvenile survival was very low in both 2014 and 2016, which may be due to unusually high flows during spawning and/or incubation periods in each year.
Marine survival of unfed fry released from the Quinsam hatchery range from 0.2% to 0.4% (yes, that is less than 1%) (Ewart & Anderson 2013).
However, based on data from Welch et al. 2020, survival of coded wire tagged chinook in the Quinsam ranged from a low of 0.056% in 2007 to a high of 3.3% in 1977, with an overall mean of 0.74%. Mean survival since 2000 is lower (0.28%, 0.56% to 0.56%). These estimates are generally within the range of other hatchery released sub-yearling populations within the straight of Georgia (see image below using data from Welch et al. 2020).
Figure 10: Survival of coded wire tagged Chinook sub-yearlings (Age-0 upon release) released from hatcheries throughout the Strait of Georgia, including the Quinsam River. Note that y-axis is log transformed to better see range of values (labels are actual values). Figure prepared using data prepared by Welch et al. 2020
Welch et al. 2018 used coded-wire tag data to look at large scale patterns of Chinook salmon survival. This data demonstrates that survival collapsed over the past half century by a factor of ~3 and is currently ~1% in many regions (consistent with estimates available for the Campbell). Survival in relatively pristine and undeveloped regions (e.g. Northern BC and Alaska) was comparable to areas with extensive water management and land development that were previously considered to have poorest survival (e.g. Columbia River). The authors suggest the widespread trends in survival may be evidence that marine conditions are more influential than local factors (e.g. freshwater habitat).
Similar trends have been observed in other species. For example, Price et al. 2021 found a 69% reduction in wild Sockeye salmon returns (though overall returns are comparable to historic levels due to intensive enhancement); that population diversity has decreased by ~70%, and; that life history diversity has shifted with populations now migrating from freshwater earlier and remaining at sea for longer.
Interestingly, hatchery releases have never been higher
.
Off the top of my head, there are four things that are most likely to be affecting catches of Tyee salmon (in reality, there are many, many more. But for now let’s start with this).
Generally, juvenile recruitment refers to the process of small fish transitioning to an older life stage (e.g., an egg hatching into an alevin, a fry becoming a parr or smolt, a smolt maturing into an adult…). According to Thornton et al. 2022 Campbell River Chinook fry emerge in February-March and out migrate as Age-0+ juveniles from March through July. Smaller recently emerged Age-0+ fry are dominant and typically captured from March through early May (37 to 52 m) While larger Age-0+ smolts are less common and move out from May through July (64 to 88 mm). Given that Chinook move to the estuary as fry, lets figure out how many fish should be produced each year. To do this, we need to know:
So under normal conditions we could expect to see annual fry production ranging from 42,066 to 616,967, with a mean of 271,962 fry.
But abnormal is the new normal, so let’s look at the extremes. High flows through the incubation period can greatly reduce survival by scouring away gravel and eggs. Thornton et al. 2022 observed this in 2016 when very few Chinook (or other salmon) fry out migrated following a large spill event in November 2016 (and to a lesser extent in 2014).
If we assume that flows over 375 cms reduce fry out migration by 90% we see that fry production in years with high flow events is greatly reduced, which will have significant effects on future returns (Note that I have no idea what flows are required to scour gravels in the Campbell or what associated mortality would be, this is purely speculative. AND, mortality rates are likely to vary relative to flow (e.g., 375 cms may result in 75% mortality, 500 cms produces 85% mortality and 600+ results in 90% mortality). If we apply this assumption, we get the figure below, which shows how high flows may reduce juvenile recruitment.
Although major flow event that reduces egg-to-fry survival will reduce escapement, there is a silver lining. Given the age structure of Campbell River Chinook, the resulting reduction in escapement will be spread across multiple years. Arguably, this is a great example of bet-hedging. If all fish returned as Age-5 fish (which would be advantageous biologically since larger fish produce more eggs), then a high flow event could essentially wipe out a full cohort. Having a population returning at different ages ensures that fish return each year, even if something reduces survival of a single age-class or cohort.
Figure 11: Estimated annual Chinook Salmon fry production in the Campbell River, peak flows during incubation period and estimated impacts of high flow events throughout the incubation period.
Well, I am already going out on a limb here. Key takeaway here is that high flow events during sensitive spawning and incubation periods are likely to have a detrimental effect on juvenile survival, which in turn will contribute to a reduction in the number of Tyee that I fail to catch. But, an event that reduces survival will in a single year will not wipe out the run as fish are returning at different age classes.
Overall, Ewart & Anderson, 2013 have estimated marine survival in the Campbell River system is approximately 0.003.
Coded wire tag data reviewed by Welch et al. 2022 marine survival of Quinsam Chinook released as fry from 1974 to 2014 ranged from 0.056% in 2007 to 3.3% in 1977, with an overall mean of 0.74% (2014 release group was 0.55%, which is best it has been since survival rate since 1998).
. This stuff is all way more complicated than I want to get into. For now I will pretend that marine survival stable (spoiler, they are not).
For now, I am going to assume effort (# of boats fishing per tide/day) is constant and that catchability (percent of Tyees present that are captured) is stable. In reality, I would guess that effort has likely decreased over time and catchability has likely increased as peoples knowledge, skill and fishing technology have improved over time (not everyone though, I still suck). Either way, without some hard data there is not much I can do with this.
Tyee fishermen may be among the toughest of tough (cough, cough), but even so, windy, wet seasons are likely to result in lower effort and fewer fish than relatively drier, calmer seasons. It is also possible that fish behaviour will change in response to river conditions. Certainly there was a lot of speculation that high flows during the 2022 Tyee season contributed to record low catches.
For now, I have little interest in combing through historic weather data. But, I already have flow data. So let’s see how river flows have varied between seasons.
7.9% of fish will return as Age-3, 44.7% of fish will return as Age-4 fish, 46.1% will return as Age-5 fish and 1.3% will return as Age-6 fish (Sturham et al. 1999).
All fish captured in the Tyee pool are actually from the Campbell system.
We can expand this to estimate the number of Tyee salmon that will return if we make even more assumptions!
Note, this is where shit is going to get weird. At this point I am mostly just making shots in the dark and everything should be considered very skeptically.
Off the top of my head there are two ways we can approach this:
1.) How many fish should come back based on past on escapement counts and available biological data.
2.) We can look at what factors influenced how many fish were available for capture in the Tyee pool (i.e. how historic conditions may have contributed to observed captures), and/or;
3.) We can look at what factors influenced how returning fish were captured (i.e. conditions during the fishing season)
We can VERY CRUDELY estimate the number of salmon that should return to the Campbell River if we make a couple of big assumptions:
Fecundity is ~5,700 eggs per female (Ewart & Anderson, 2013)
Sex ratios are 60:40 female to male using (Sturham et al. 1999) data for Campbell River.
Egg-to-fry survival is approximately 0.1, can’t recall where this number came from but its commonly used as a measure of egg-to-fry survival of wild fish (compared to 0.9 for hatchery reared fish). Give results from Thornton et al. 2022 it is likely that egg-to-fry survival in the Campbell is higher.
Marine survival (smolt to adult) is approximately 0.003 (Ewart & Anderson, 2013)
7.9% of fish will return as Age-3, 44.7% of fish will return as Age-4 fish, 46.1% will return as Age-5 fish and 1.3% will return as Age-6 fish (Sturham et al. 1999).
All fish captured in the Tyee pool are actually from the Campbell system.
We can expand this to estimate the number of Tyee salmon that will return if we make even more assumptions!
If we run these numbers, each female will generate 1.7 offspring, of which 0.14 will be Age-3, 0.76 will be Age-4, 0.79 will be Age-5 and 0.022 will be Age-6. Furthermore, each female will produce 0.24 Tyee salmon. Let’s take a moment to remember that these assumptions are terrible. Larger fish are more likely to produce larger fish, so in reality some fish will produce a decent number of Tyee and others will produce none. But let’s keep it simple for now and assume every fish is able to make an equal number of Tyees
Based on this, each female should produce 1.7 offspring that return to spawn. Which is less than ideal.
Figure 12: Predicted returns of Campbell River Chinook by age-class relative to measured escapement (does not include Quinsam River fish).
Well that’s interesting. There are periods when my predicted returns closely align with actual escapement (most closely from 2003 to 2007, but my values are comparable from 2003 to 2010). This suggests my estimates may not be WAY off but does not confirm they are correct. Other notes:
Let’s look at little closer at how many Tyee salmon may be returning in a given year.If all Tyee salmon were captured each year, we would be actively selecting against large fish, so we would expect to see a rapid and continuous decline in the total number of Tyees returning each year (which I suppose we are). But, I have had the opportunity to snorkel the Campbell River canyon a number of times and have seen spawning Tyee, and last year there were lots of Tyee captured in the river… though not sure what their fate was. Aynways, all this to say that its unlikely every Tyee is captured in the pool, and the actual number returning to the pool should be at least equal to or higher than the number captured.
Reminder of key assumptions in the plot:
Figure 13: Comparison of catches of Tyee Salmon, predicted returns of Tyee Salmon and annual Chinook Salmon escapement counts.
Well, this figure either shows how poor my estimates are, or that a tremendous number of Tyee are intercepted (e.g. marine survival of Tyee salmon is lower than other fish).
Figure 14: Chinook Salmon escapement from rivers on East and West Coast of Vancouver Island.
Well, that figure sucks. But it shows how variable escapement is between years. On the East Coast of the Island, abundance increased in 43% of plotted streams and decreased in all others. Decreases
Relative to 2013, abundance in all plotted west coast streams was slightly reduced in 2014. There was a major crash in the Burnam River, but this is exaggerated by unusually high returns in 2013, 2015 and 2016.
Figure 15: Catches of Tyee Salmon since 2016 relative to flow in the Campebll River.
Well, it’s clear that flows in 2022 were higher than past years and higher than mean flows over the past 5-years. But this doesn’t mean that is why fewer fish were captured.
Last year there was a lot of speculation that high flows in the Campbell River may have caused fish to move directly into the river rather than staging in the pool. Let’s look at flow in the Campbell River to see how 2022 flows compared to previous years.
## `geom_smooth()` using method = 'loess' and formula = 'y ~ x'
Figure 16: Relationship between river flow and fish capture
Figure 16 suggests flows below ~ 25 cms are favourable and that higher flows will result in fewer fish, As one would expect. Fish are more likely to remain within the pool while flows are low and will move into the river when flows are higher and they can safely navigate upstream. However, the fishery occurs during the late summer, when flows are typically low. So it’s somewhat of a chicken and egg situation….
OK, well there is a relationship (that could be due to a number of things). Lets have a look at some of the older data.
Let’s look at commercial catches. Maybe there is a fishery that could be intercepting a large number of Tyees.
###Notes Plot peak flows 4 to 5 years previous (e.g. impact of peak flows on recruitment). - Assume mortality at >200 cms - spawning habitat lost at 300-400 cms - Is Quinsam flow regulated? Ask Mary.
Is return age genetic? Or environmental?
| Waterbody | Sex | Age | n | % of Total (by Sex) |
% of Total (by Stream) |
Size Range (mm) |
Mean Lenght (mm) |
Std. Error |
|---|---|---|---|---|---|---|---|---|
| Campbell River | F | 3 | 0 | 0.00 | 0.00 | 500 - 699 | 595 | 20.82 |
| Campbell River | M | 3 | 6 | 0.19 | 0.08 | 500 - 699 | 595 | 20.82 |
| Campbell River | F | 4 | 21 | 0.48 | 0.28 | 700 - 899 | 783 | 10.69 |
| Campbell River | M | 4 | 13 | 0.41 | 0.17 | 550 - 949 | 776 | 23.30 |
| Campbell River | F | 5 | 23 | 0.52 | 0.30 | 750 - 949 | 839 | 7.51 |
| Campbell River | M | 5 | 12 | 0.38 | 0.16 | 700 - 949 | 846 | 14.43 |
| Campbell River | F | 6 | 0 | 0.00 | 0.00 | 900 - 949 | 930 | 0.00 |
| Campbell River | M | 6 | 1 | 0.03 | 0.01 | 900 - 949 | 930 | 0.00 |
| Quinsam Hatchery | F | 3 | 9 | 0.04 | 0.02 | 550 - 749 | 644 | 15.33 |
| Quinsam Hatchery | M | 3 | 67 | 0.38 | 0.18 | 400 - 749 | 595 | 6.84 |
| Quinsam Hatchery | F | 4 | 130 | 0.65 | 0.35 | 600 - 899 | 742 | 3.77 |
| Quinsam Hatchery | M | 4 | 95 | 0.54 | 0.25 | 550 - 899 | 745 | 5.64 |
| Quinsam Hatchery | F | 5 | 61 | 0.30 | 0.16 | 700 - 949 | 823 | 5.76 |
| Quinsam Hatchery | M | 5 | 12 | 0.07 | 0.03 | 750 - 949 | 845 | 13.57 |
| Quinsam Hatchery | F | 6 | 1 | 0.00 | 0.00 | 800 - 849 | 812 | 0.00 |
| Quinsam Hatchery | M | 6 | 1 | 0.01 | 0.00 | 750 - 799 | 756 | 0.00 |
| Quinsam River | F | 3 | 1 | 0.01 | 0.00 | 700 - 749 | 700 | 0.00 |
| Quinsam River | M | 3 | 45 | 0.41 | 0.22 | 500 - 849 | 626 | 12.07 |
| Quinsam River | F | 4 | 58 | 0.63 | 0.29 | 650 - 849 | 744 | 4.73 |
| Quinsam River | M | 4 | 56 | 0.51 | 0.28 | 550 - 949 | 723 | 9.35 |
| Quinsam River | F | 5 | 31 | 0.34 | 0.15 | 700 - 949 | 830 | 7.54 |
| Quinsam River | M | 5 | 9 | 0.08 | 0.04 | 700 - 949 | 806 | 21.00 |
| Quinsam River | F | 6 | 2 | 0.02 | 0.01 | 800 - 849 | 838 | 2.83 |
| Quinsam River | M | 6 | 0 | 0.00 | 0.00 | 800 - 849 | 838 | 2.83 |